1. Field of the Invention
The present invention relates to a multi-gate transistor device, and more particularly, to a green fin field effect transistor (FinFET) device based on quantum mechanical tunneling effect.
2. Description of the Prior Art
Complementary metal-oxide-semiconductor (CMOS) field effect transistor is one of the core elements of the integrated circuits (ICs). As dimensions and operation voltages of CMOS device are continuously reduced or scaled down, higher performance and packaging density of the ICs are achieved. However, it is found that the power consumptions of CMOS device keeps increasing because the off-state leakage currents are increasing and a fact that the subthreshold slop is limited to minimally about 60 mV/decade. Therefore, there has been developed the tunneling field effect transistor (hereinafter abbreviated as TFET) device as a countermeasure against to the abovementioned problem.
Please refer to FIG. 1, which is a schematic drawing of a conventional TFET device. Different from the conventional MOSFET device of which the source and drain have the same conductivity type, the TFET device includes the source and drain having different conductivity types. As shown in FIG. 1, the conventional TFET device 10 includes a substrate 12, a gate structure 14, an n-type source 16 and a p-type drain 18 (or a p-type source 16 and an n-type drain 18). As well-known to those skilled in the art, the conventional TFET device 10 fully controls source tunneling barrier and may act as either an n-channel device or a p-channel device depending on the gate voltage applied to the gate structure 14.
Please refer to FIGS. 2A and 2B, which respectively show a band diagram of the conventional TFET device in the OFF-state and the ON-state. As shown in FIG. 2A, when the TFET device 10 is in the OFF-state, the gate bias voltage is zero with insufficient band bending to allow tunneling and thus the leakage current is extremely low. When the TFET device 10 is in the ON-state, sufficient band bending is caused and thus electrons tunnel through from the valence band of the p-source to the conduction band of the n-drain. Since the TFET device has the advantages of low off-state leakage currents and low power consumption, it is taken as a promising green device in the future semiconductor industry.
Nevertheless, though the TFET device efficaciously solves the off-state leakage currents problem, it cannot be scaled down as expected due to the short channel effect (SCE). Besides, the TFET device still suffers the problem of drain-induced barrier lowering (DIBL) leakage.
Therefore, it is still in need to develop an approach that is able to solve the aforementioned power consumption problem, to suppress SCE and DIBL leakage, and to keep scaling down the device.